In general, an electric motor with a brush (hereinafter abbreviated as a motor where appropriate) is often used as a drive source for a wiper device secured to a vehicle such as a car. A motor of this kind has a structure in which an armature with an armature coil wound around the armature is located to be rotatable inside a cylindrical yoke having an inner circumferential face equipped with magnets. The armature has an armature core engaged on and fixed to the outside of a rotation shaft. Plural long slots elongated in the axial direction are formed in the armature core. Winding wires are wound between these slots at predetermined intervals, to form plural coils. The coils are electrically conducted to commutator members attached to the rotation shaft. The commutator members slide on a brush, and supply electricity to the coils via the brush, thereby generating a magnetic field. The rotation shaft is driven by magnetic suction force and repulsive force which are generated between the commutator members and the magnets of the yoke.
In the motor as described above, for example, coils are formed as follows in case of having two poles and twelve slots. FIG. 11 is an exploded view of an armature in which numerals 1 to 12 are respectively assigned to twelve commutator members 51, as well as twelve teeth 52. As shown in FIG. 11, for example, a winding wire 53A is wound out from the third commutator member. The winding wire is wound n turns (plural turns; for example, 66 turns) between a slot 54a and another slot 54f to form a coil 55A, where the slot 54a exists between the first and second teeth and the slot 54f exists between the sixth and seventh teeth. Thereafter, the winding wire is connected to the fourth commutator member. Next, another winding wire 53B is wound out from the fourth commutator member, and is then wound plural turns between a slot 54b and another slot 54g to form another coil 55B, where the slot 54b exists between the second and third teeth and the slot 54g exits between the seventh and eighth teeth. Thereafter, the winding wire is connected to the fifth commutator member. Likewise, winding wires 53 wound out from respective commutator members 51 each are wound plural turns between slots, to form coils 55. Thus, plural coils 55 are, formed around the armature core.
Meanwhile, a motor used as a drive source of a wiper device is requested to perform high-speed rotation operation so as to cope with heavy rain and the like, in addition to normal operation which produces predetermined rotation output. That is, a motor for a wiper device needs two operation modes for a normal (low) speed and a high-speed. Besides, both operation modes have to be switched quickly from one another. In this motor, hence as shown in FIG. 12, a high-speed brush 62 used for high-speed operation (HI) is provided in addition to a low speed brush 61 used for normal operation (LOW). The rotation speed of the motor is changed by switching the brushes.
The low speed brush 61 and the high-speed brush 62 each coupled with a common brush 63 and form respectively pairs of brushes. The brushes 61 to 63 each slide on a commutator 64. During normal operation, the common brush 63 and the low speed brush 61 supply power. On the other side, during high-speed operation, either an anode brush or a cathode brush is switched to the high-speed brush 62, so that the common brush 63 and the high-speed brush 62 supply power. The high-speed brush 62 is located at a position shifted by an angle a in a rotation direction from the low speed brush 61. During high-speed operation, the motor is subjected to lead angle control so that the rotation speed increases higher than during normal operation. High-speed wipe operation can then be performed. Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 2002-305861